Weighted vests are a specific form of Sensory Integration Therapy (SIT) (Honaker, 2005a) that are intended to help individuals resolve sensory related issues thereby decreasing the symptoms (e.g., hyperness, lack of attention, etc.) of the sensory issue and are also often recommended as an intervention for problem behaviors exhibited by children with Pervasive Developmental Disorders (PDD). The effects of 5% and 10% total body weight vests on problem behaviors in children with PDD were investigated during functional analysis conditions (Iwata, Dorsey, Slifer, Bauman, & Richman, 1982/1994). Though results indicated there was no functional relationship between the SIT of 5% or 10% weighted vests and participants' problem behaviors, a further analysis indicated there was a functional relationship between the problem behavior and the operant-based intervention of functional communication training. Thus, though the problem behaviors appeared to be unresponsive to SIT (i.e., weighted vests) these same problem behaviors could be altered with interventions that have been grounded in rigorous, empirical scientific research findings. (Contains 3 figures.)